licenses: convert license tags to SPDX

global: isabelle update_cartouches

lib: update for Isabelle 2019

Isabelle2018: new comment syntax

(result of "isabelle update_comments <dirs>")

globally use session-qualified imports; add Lib session

Session-qualified imports will be required for Isabelle2018 and help clarify
the structure of sessions in the build tree.

This commit mainly adds a new set of sessions for lib/, including a Lib
session that includes most theories in lib/ and a few separate sessions for
parts that have dependencies beyond CParser or are separate AFP sessions.
The group "lib" collects all lib/ sessions.

As a consequence, other theories should use lib/ theories by session name,
not by path, which in turns means spec and proof sessions should also refer
to each other by session name, not path, to avoid duplicate theory errors in
theory merges later.

Removes all trailing whitespaces

fewer warnings

infoflow: weakened assumptions for c refinement of infoflow adts

The fact that the C infoflow adt refines the abstract infoflow adt now only requires that given user operation is nonempty and not sane (nonempty and doesn't return an interrupt).
Also added some more general lemmas about fw_sim and refinement to lib/Simulation.thy.

Import release snapshot.